The presence of swine flu in Mexico and the United States is "a serious situation" that could develop into a pandemic, the World Health Organization's director-general said Saturday. "This is an animal strain of the H1N1 virus and it has pandemic potential because it is infecting people," Dr. Margaret Chan said Saturday speaking to reporters by phone.

Mexico City has closed all of its schools and universities until further notice because of the virus, and on Saturday, the country's National Health Council said all soccer games would be played Saturday without public audiences

Asked whether the committee would address raising the agency's alert concerning the virus to 6, a pandemic alert and the highest level on WHO's scale, Chan said, "Yes, indeed."

The alert stands at 3, meaning "No or very limited human-to-human transmission."

Chan said Saturday that WHO does not have indications of similar outbreaks elsewhere.

However, she said, "The situation is evolving quickly. A new disease is by definition poorly understood."

White House spokesman Reid Cherlin said Saturday that the White House was taking the situation "seriously and monitoring for any developments."

Health officials in Texas announced Saturday the temporary closure of Byron Steel High School in Cibolo, Texas, where swine flu was confirmed in two students earlier this month.

The United States had not issued any travel alerts or advisories [consider not traveling to Mexico] by late Friday, but some private companies issued their own warnings.

Mexico’s Health Secretary Jose Angel Cordova said the country has enough Tamiflu to treat 1 million people — only one in 20 people in greater Mexico City alone — and that the medicine will be strictly controlled and handed out only by doctors.

There are many things you can to do preventing getting and spreading influenza:

There are everyday actions people can take to stay healthy.

* Cover your nose and mouth with a tissue when you cough or sneeze. Throw the tissue in the trash after you use it. * Wash your hands often with soap and water, especially after you cough or sneeze. Alcohol-based hands cleaners are also effective. * Avoid touching your eyes, nose or mouth. Germs spread that way.

Try to avoid close contact with sick people.

* Influenza is thought to spread mainly person-to-person through coughing or sneezing of infected people. * If you get sick, CDC recommends that you stay home from work or school and limit contact with others to keep from infecting them.

The United States Government has reported seven confirmed human cases of Swine Influenza A/H1N1 in the USA (five in California and two in Texas) and nine suspect cases. All seven confirmed cases had mild Influenza-Like Illness (ILI), with only one requiring brief hospitalization. No deaths have been reported.

The Government of Mexico has reported three separate events. In the Federal District of Mexico, surveillance began picking up cases of ILI starting 18 March. The number of cases has risen steadily through April and as of 23 April there are now more than 854 cases of pneumonia from the capital. Of those, 59 have died. In San Luis Potosi, in central Mexico, 24 cases of ILI, with three deaths, have been reported. And from Mexicali, near the border with the United States, four cases of ILI, with no deaths, have been reported.

Of the Mexican cases, 18 have been laboratory confirmed in Canada as Swine Influenza A/H1N1, while 12 of those are genetically identical to the Swine Influenza A/H1N1 viruses from California.

The majority of these cases have occurred in otherwise healthy young adults. Influenza normally affects the very young and the very old, but these age groups have not been heavily affected in Mexico.

Because there are human cases associated with an animal influenza virus, and because of the geographical spread of multiple community outbreaks, plus the somewhat unusual age groups affected, these events are of high concern.

The Swine Influenza A/H1N1 viruses characterized in this outbreak have not been previously detected in pigs or humans. The viruses so far characterized have been sensitive to oseltamivir, but resistant to both amantadine and rimantadine.